Matching your load requirements to the board volume you're purchasing is crucial.
This will ensure you're making the right choice for your needs.
Not only do you need to consider your body weight, but other factors such as:

• Will I want to paddle with my kid/s?
• Will I want to paddle with my dog?
• Will I need to take provisions with me?
• Who else will want to use the board?

INFLATABLE BOARD VOLUMES are generally higher than hardboard equivalents.
When we say a 6" thick Drop Stitch PVC Material, the board is consistently 6" thick throughout.

The uniform thickness, unique to inflatable boards, is not just a feature but a critical factor in their buoyancy and performance.
This sets them apart from hardboards in terms of their load-carrying potential.

GENERALLY WE CAN SAY 6" INFLATABLE BOARDS ARE HIGH IN VOLUME 
For instance, a 4.75 Drop Stitch PVC Material used on some inflatable boards means a lowered volume, directly impacting the board's performance.
Understanding this difference can help you make an informed decision. 

NOTE: Hardboard thickness varies considerably within one design. 
Because of this, hardboards often have areas of high and low volume along their length, depending on the thickness x width ratios.

Because of this important consideration, we use a simple formula.
Within this formula, we must consider that for every 1L of volume, it requires 1kg to sink it!
This means you need a lot more volume than you have in equivalent kilograms acting downwards on the board.

Ideally, you want the board to have at least 40-50% residual volume to float and perform.
Performance may not always be an essential factor, but floating indeed is!

What is ‘optimum max load capacity’
It's the maximum weight the board can carry while performing at its best in performance and handling.

What is ‘max load capacity’
The board's performance will decrease between ‘optimum max load’ and ‘max load capacity’.
When it reaches 'max load capacity,' it is said to be at its limits of use and performance.

GUILD REFERENCE

The Guild Reference for Stand-Up Paddleboards presents a formula for the optimum board volume relative to weight and skill levels.

Determine the optimum max load capacity of an inflatable paddleboard.

Board Volume in Litres ÷ 1.2
Divide this figure by 2.2 to convert it to Kg
i.e. 300L ÷ 1.2 (250) ÷ 2.2 = 113kg
Round down to 110 kg

To Determine the max load capacity of an inflatable board

Board Volume in Litres divide by 2.2 to convert to Kg
i.e 300L ÷ 2.2 = 136 kg
Round down to 135 kg

With this simple formula, you can calculate any given paddleboard volume relative to its load-carrying potential.
NOTE: This formula applies to recreational inflatable paddleboards and hardboards, as well as touring and racing. The formula for SUP surfboards differs.